Alternator whine question

[smashman]

Hey guys,

2001 RT/10

I recently installed a new head unit and pre-amp and I am getting some alternator whine. Not excessive, but enough to be annoying. My amps and pre-amp share a common ground using a distribution block in the trunk. The head unit I grounded to a metal piece behind the dash and I'm thinking that may be the issue. The original din plug/cable that connected the factory Alpine unit to the factory amp in the trunk is still intact, but not connected to anything at either end. (I replaced a Pioneer aftermarket head unit, and I stupidly admit, I don't recall where the ground wire from that one ran to)

Another thread mentioned that the #8 pin on the din plug was the ground. Does that ground wire only go straight from the head location back to the other end in the trunk, or does it branch off and ground to the chassis somewhere?

I am thinking I could tap into that wire behind the dash without any issue, I'm just wondering if I then would also need to tap into it in the trunk and run it to my ground distribution block there?

Thanks.

 

[smashman]

OK, I checked again and the ground actually already does tap into the correct ground wire on the old white connector from the stock radio, which according to the service manual that ground terminates at location #G203 under the dash. I mixed up where I had grounded the head unit with what I did with my daughter's car. I may try to run a second ground to a metal piece behind the dash and see if that helps at all. Any other thoughts appreciated.

 

[Steve M]

Only time I've ever run into this in the past was when my power and signal wires were running parallel directly on top of each other nearly the entire length of the car.

I separated them out distance-wise as best I could, and if they had to cross, I made sure it was as close to 90 degrees as possible.

I'm not sure what helped the most, but I didn't have issues after that in any of the vehicles in which I have installed aftermarket stereos (3 total), some of which have had multiple iterations of equipment.

 

[Steve-Indy]

Agree with what Steve M said...side by side, parallel wires are an issue. This recalls to mind a "high end, custom" stereo shop/installer here in Indy who rigged the the wiring in a similar fashion as Steve described..."hum" was the result. Owner rewired it with a perfect outcome.

Another point to consider: not every "metal piece" under/behind the dash of a Viper is an adequate ground.

 

[smashman]

Thanks for the replies, guys. Still working on this. I had no whine at all with the previous Pioneer head unit. I had no whine when the new Kenwood head unit was installed, using the same oem ground wire as the Pioneer. It's a pretty sad little ground wire, to be sure.

The whining started when the Matrix pre-amp was installed, which only required adding a short run of RCA's to the preamp, about 3 ft to the pre amp sub inputs and the same back to the sub amp. For the front channel, the existing RCA plugged into the preamp input, and the RCA back to the front channel amp is only 1 foot. The pre-amp only requires a small power wire with a 1 amp fuse, ground wire, & remote wire and it's grounded to the same distribution block as the 2 amps. The power wire runs to the same distribution block as the amp power wires. For the remote wire, I tapped into the remote wire for the front channel amp.

I don't hear any whine from the sub, but it may be there and the frequency is just too high to hear it.

If I run the existing Front channel RCA directly to the amp and bypass the pre-amp, the whine goes away. Which makes it seem like something with the pre-amp may be the issue, but it could be that the pre-amp is simply juicing up noise from somewhere between the head unit & pre-amp.

I have tried just laying the new RCA cables along the trunk carpet, completely away from any power wires, and it makes no difference.

I did do a second ground wire for the head unit and it made it worse, so that will be undone. Agreed, not every piece of metal is a good ground point, but it was accessible, so it was worth a shot. Two different grounds may not be a good idea?

Next diagnosis steps, please add any advice, it's very welcome:

1. The pre amp is pretty close to the Front channel amp. I can easily dismount it and move it further away and see if that helps.
2. Disconnect all RCA's from the head unit and see if noise remains. If not, plug them back in one by one and see if noise comes back.
3. Run a test ground wire from the head unit back to the ground block in the trunk, so all components have a common ground. If that works, at least I'd know the problem is the head unit ground and can proceed from there.
4. I used rubber spacers between the deck "L" brackets and the metal mounting points when mounting the deck so it would sit flush so I would not have to drill new holes in the stock "L" brackets. I will either try metal spacers or drill new holes in the "L" brackets so I have metal to metal contact, thus the deck chassis can act as an additional ground.
5. Try different RCA cables. The ones I used are Recoil. I tried some J&D's from Amazon and same whine, but lowered sound quality. I spoke to Dan at KnuConcepts and he says he doesn't believe it's the RCA's but that their Krystal cables or cables with a larger conductor may actually exacerbate the problem if it is. Which is somewhat confusing to me as the more expensive cables are touted as having better shielding, etc.
6. Tap the pre-amp remote wire to a different location. There is an empty slot in the fuse box in the trunk for the factory amp. Does anyone know if that is switched or hot all the time?
7. I play my music from a USB. I tried a different USB, no difference. The Kenwood deck has the USB cable integrated and it's long and a lot of extra. (Dumb design) Not sure if that could be picking up noise. I will try the USB port on the front of the deck and see if that makes a difference. Maybe it's something that simple.
8. Unplug the antenna from the head unit and see if the noise goes away.


If none of this works, I may have to go back to Crutchfield and exchange deck and/or pre-amp in case one of those was just bad out of the box. I hate to ditch the pre-amp altogether, it really makes a huge difference.

Sorry for such a long post, but I wanted to provide as much info as possible.

Thanks again for any suggestions.

 

[Bigsnow]

Let me know what you find.... following. (Me too)

 

[phipplet]

This is interesting. I was having similar alternator / charging issues. Put an aftermarket alternator on, still didn’t work. It would act like it was charging fine initially for about 30 mins. Then the battery wouldn’t hold the charge and die. Wound up being the Optima battery I purchased last year. Did a little research and I guess these batteries are no longer what they used to be. Switched out the Optima with another brand! All fixed! Not sure what battery you are using.



I put the original alternator back on. No problems.

 

[smashman]

OK, here is what I have done so far:

1. Move Matrix pre-amp further away from front channel amp: No Effect.
2. Changing the rubber spacers will not matter-the flat area where the "L" brackets contact the vehicle is plastic, not metal.
3. Tried front USB vs rear: No Effect.
4. Unplugged antenna from head unit: No Effect.
5. Ran front and rear RCA cables directly to pre-amp inputs, bypassing existing RCAs: No Effect.

Disconnecting the RCAs from head unit one by one did create some effects:

With all 4 RCAs connected, the whine is very faint. As soon as I disconnect one of the RCAs, it gets far worse. The two RCAs for the front have the most pronounced effect, as soon as either of those is disconnected, the whine probably triples in volume. As I disconnect the remaining 3 the whine lessens but is still present with all 4 rca's unplugged. It's the worst when one of the front channel ones is unplugged, and the other three remain plugged in. (I don't have any thing plugged to the rear channel outputs, only the fronts)
But plugging the cables into or getting them close to the rear output plugs caused noise changes just like with the front.

I'm not sure what is the next logical step, does anyone have any thoughts? It doesn't seem like it would be the cables themselves, as using different ones didn't solve the issue, but I'm going to go test my existing rca's with a multimeter and see if there is any indication of excess resistance or a short.

 

[Goggles Pizano]

What is your gain set to?
Your RCAs are they shielded?
And what was the reason to install a pre-amp (i looked at your other threads quickly but didn't see anything)?

You may need a power line filter. But your gain is probably set too high (you mentioned in the other thread your amp gain it set to lowest). There is a method and equipment to set gain but you can set it pretty decent using a multimeter

 

[Goggles Pizano]

Also ground your pre-amp to the head unit.
If that doesn't work assuming you ran the cables in new paths, power the pre-amp from a different power supply/source (i.e. separate battery just powering the preamp).

 

[smashman]

Thanks for the responses, Goggles.
The gain on both amps is at dead minimum.
The RCAs run under the center console and the power wires run from the battery in the back. They are all separately split-loomed. There is a very short distance where they are parallel in the trunk. I have undone the zip ties and completely separated them to test and it makes no difference.
I don't know if the RCA's from the head unit to the trunk are shielded, as they were installed by Car Toys 22 years ago. I can see through the sheathing and they appear to be twisted pair RCAs. The ones I tried as a test directly from head unit to trunk are new and definitely shielded and it made no difference.
I installed the pre-amp because the sound from the new deck was somewhat anemic. Turning up the gains on the amps to compensate introduced more distortion. The old deck had 6.5 volt pre-outs. The new one has 5 volts.
I have a line filter on the yellow battery wire that goes to the head unit.
The pre amp has lights that show the voltage it is putting out. 1, 2, 5, and Maximized. I checked with Rockford Fosgate and they said my amps can handle 4 volts input.

The gains on the pre-amp are a little over halfway up. I set them using the method below:
Head unit volume to just below distort level, which on the Kenwood is around 23-24.
Rca outputs from pre-amp not connected to amps yet.
Play several songs with full and clean vibrant sound and good bass.
Increase pre-amp gain for front channel until 5 volt light flashes on bass hits, then back off until only 2 volt light flashes on bass hits.
Repeat process for pre-amp sub output.
Connect Rca's from pre-amp to front channel amp & fine tune pre-amp gain
Repeat for sub channel.
Fine tune with head unit EQ, (crossover, slope, etc)
The sound is excellent. At head unit volume 22 it's crystal clear, full and rich, no distortion, even on hard rock songs with lots of screaming guitars. The sub is deep and thumps well, but it's not over extruding at all.

Since my last post, I ran a ground directly from the head unit to the ground distribution block in the trunk, so all components have a common ground. (Does that accomplish "grounding the pre-amp to the head unit"?) That seemed to help somewhat with the whine, (not much) but it caused the sound quality to degrade. Perhaps the head unit ground is too long that way. I also tested my RCAs from head unit to trunk for continuity with a multimeter and they checked out.

The problem seems to be centered where the RCAs plug into the deck, as described in my previous post. The antenna plugs in right next to the RCAs and after running the longer ground wire, I noticed an increased whine when the antenna was plugged in. I know a thin wire can be wrapped around the RCA's and grounded to the deck chassis, and I may try that, but it may be that I got a lemon head unit where the RCA ports aren't grounded correctly.

Tomorrow I will try powering the pre-amp separately from the amps, as you suggested. I also inspected inside the dash, and I can see the nut where the oem deck ground ends up. I am going to try running the deck ground directly to that location and see if that helps. The ground wire in the OEM harness is really thin and maybe a thicker and direct ground would help.

Thanks again for the advice, I will continue to update.

 

[smashman]

Hey guys, it's been 10 days since update, had some other obligations but tried several other potential fixes:

Ran thicker ground wire directly to stock location
Powered Matrix off of a separate battery
tried Inline Noise filter to yellow battery "in" wire
tried ground loop isolator on both sets of RCA outputs
Dismounted matrix, moved away from amp
wrapped bare wire around all RCA outputs & grounded to deck chassis
tried usb on front deck input vs rear on the cable

None of these made any difference at all.

Grounding the head unit back to the same trunk location as the amps & preamp reduced noise somewhat, but it's still there and too much. Plus, when I plug the antenna in the noise gets much worse. The antenna input is right next to the RCAs on the deck. I also tried leaving the ground wire free and just using the antenna as a ground. The deck functioned, but the whine was worse that way.

The only other thing I can think of is to ground the deck right to the negative terminal on the battery, which would be fairly simple as I could just attach it to the lug on the negative disconnect switch that runs to the negative battery terminal.

I could also remove the back tire again and re-check the negative cable that grounds to the vehicle chassis under there, but I'd think if that ground were bad, I'd be having many other issues besides just alternator whine.

In any case, Crutchfield is sending me a replacement deck, as it's possible the one I got might just be a lemon from the get go and might have grounding problems internally at the rcas or antenna input location.

I'll continue to update, but any ideas are very welcome.

 

[Goggles Pizano]

I will PM you a full test procedure as you doing a lot of things or will just post it here.

 

[smashman]

PM or post, either would be very appreciated!

 

[Goggles Pizano]

PM''d

 

[99RT10GTS]

I have a new, in the box, Mopar Alt if you want to try a different one.

 

[smashman]

99RT10GTS, Thank You, and I will keep that in mind for sure. I don't suspect the alternator is the culprit, as the previous aftermarket HU did not have the whine issues, but anything's possible.

 

[smashman]

Well, guys, I hate to admit defeat, but I gave up on the Matrix pre-amp. Goggles emailed me a step-by-step test procedure for the whole system, which I followed religiously and the pre-amp noise just could not be done away with. It is not my RCA's or any ground problems, with the pre-amp taken out of the loop there is no whine or noise at all. No matter what I tried, it put noise in the system. The steps and tests I did were far too numerous to mention all of them, but they included running the pre-amp off of a separate battery, not even tied to the vehicle at all, and the noise continued. Same procedure with the head unit. Still noise. RCA's ran from the head unit out the window to the trunk didn't help. Noise filters on all deck and pre-amp power lines didn't help. Ground loop isolators. Nope. Changing the ground jumper inside the pre-amp. No love. Replacement head unit was exactly the same. I guess that specific pre-amp just didn't play nice with the rest of my components. Thanks for all the responses and to Goggles for the PM. I can live with the system as-is. It's still really good.